Field of the Invention
The invention relates to an image-sensor structure, and more particularly to an image-sensor structure with a conductive polymer element(s).
Description of the Related Art
An image sensor, as a kind of semiconductor device, transforms optical images into electrical signals. Image sensors can be generally classified into charge coupled devices (CCDs) and complementary metal oxide semiconductor (CMOS) image sensors. Among these image sensors, a CMOS image sensor comprises a photodiode for detecting incident light and transforming it into electrical signals, and logic circuits for transmitting and processing the electrical signals.
In an image sensor, in order to avoid crosstalk between adjacent color filters, a grid is disposed between the color filters. Generally, metal or oxide can be adopted as the material of the grid. However, a metal grid may become corroded during the color filter processes due to exposure to photoresist, developer and DI water. Furthermore, an oxide grid has a constant refractive index (about 1.46) which is incapable of further increasing the variation of the refractive index between the grid and the color filters, thus decreasing the sensitivity of devices.
Additionally, during the semiconductor processes, such as a high-speed rotation step of a wafer, electrostatic charges may be generated on the wafer. Unfortunately, the electrostatic wafer will influence in-line measurement, obtaining error data, and induce high dark current.
Therefore, development of a novel grid with an appropriate material and an adjustable refractive index (which is capable of further increasing the variation of the refractive index between the grid and the color filters) which can improve device performance such as sensitivity or SNR (signal-to-noise ratio) and effectively solve the electrostatic charge issue is desirable.